China debunks 'distorted' sulfur dioxide reading at epidemic epicentre

Data on a foreign weather website allegedly pointed to heightened levels of sulfur dioxide around Wuhan

BEIJING: The China National Environmental Monitoring Centre (CNEMC) on Wednesday refuted data on a foreign weather website that allegedly pointed to heightened levels of sulfur dioxide around Wuhan, the epicentre of the coronavirus outbreak, as "seriously distorted."

Data provided by Windy.com, a Czech company providing weather forecasting services, reportedly showed that sulfur dioxide levels in so-called "contaminated zones" of Wuhan had topped 1,500 micrograms per cubic metre early on Sunday.

Some foreign media reports picked up the incorrect data, used it as an indicator of mass cremations of bodies or medical waste, and accused China of a major cover-up.

After cross-checking Windy's off-the-charts data with those collected by monitoring centers in Wuhan run by third-party companies, the CNEMC found that the sulfur dioxide concentration in the reported areas did not even exceed 8 micrograms per cubic metre during that time.

Satellite data also showed Wuhan's peak reading of the pollutant did not surpass 11.5 micrograms per cubic metre from February 3 to 9, and the city did not see a spike in the substance when compared with surrounding areas.

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Instead, the city registered a marked drop in key air pollutants. From January 24 to February 10, the concentration of small and breathable particles known as PM2.5 dropped by 38 per cent year on year, while PM10 and sulfur dioxide plunged by 42 per cent and 22 per cent, respectively.

An unnamed CNEMC official highlighted Windy's data deviation when it comes to measuring sulfur dioxide levels in other Chinese cities.

For example, a monitoring center in Dongsi in downtown Beijing showed an average reading of 15 micrograms per cubic meter on Tuesday, while data offered by Windy.com averaged 212 micrograms per cubic metre.

Data gathered by techniques such as satellite retrieval and model simulation, both non-standardised monitoring methods, should be checked with actual monitoring on the ground and is meaningful only when its margin of error falls within a limited range, the official said.

"Windy's ground-level sulfur dioxide data was not calibrated with the actual data gathered by on-site monitoring in China, leading to figures 10 times or even 100 times greater than the actual amount," he said. "It is anything but precise."